Race Impact on Efficacy of Niraparib Plus Abiraterone Acetate and Prednisone in Patients With Homologous Repair Deficient Castration-resistant Prostate Cancer

Eligibility criteria - Prescreening Inclusion Age: ≥18 years of age (or the local legal age of consent) Participant Origin: Participants of the following origins: \- COHORT A: Participants self-identified as with black origin as defined as having origins in any of the black racial groups of Africa, as per the FDA Guidance on Collection of Race and Ethnicity Data in Clinical Trials, and irrespective of ethnicity. This includes participants with more than one race, including pardos. \- COHORT B: Participants self-identified from Native Indigenous American origins as per the FDA Guidance on Collection of Race and Ethnicity Data in Clinical Trials, irrespective of ethnicity. This includes participants with more than one race, including mestizos. OR \- Participants self-identified from White origin as per the FDA Guidance on Collection of Race and Ethnicity Data in Clinical Trials, and ethnically self-identified as Latinos. Participant and Disease Characteristics * ECOG Performance Status 0-1 * Histologically or cytologically confirmed metastatic prostate adenocarcinoma * Metastatic disease documented by conventional imaging with CT or MRI (for soft tissue lesions) or 99mTc bone scan (for bone lesions) 1. Participants with a single bone lesion on 99mTc bone scan with no other non-nodal metastatic disease must have confirmation of bone metastasis by CT or MRI. 2. Participants with lymph node-only disease are not eligible. * Willing to provide tumor tissue (archival) for determination of deleterious germline or somatic HRR gene alterations, if no local (testing done at investigator center or commercial testing) or prior sponsor-approved test result is available. 1.Testing must demonstrate pathogenic gene alterations in ≥1 of the following genes to proceed to screening: ATM, BRCA1, BRCA2, BRIP1, CDK12, CHEK2, FANCA, HDAC2, or PALB2. * Castration-resistant disease, defined by the PCWG3 as any of the following criteria while on castrate levels of testosterone (less than or equal to 50 ng/dL): 1. Visceral Progression OR 2. Bone progression (2 or more new prostate-cancer related new lesions compared to baseline) OR 3. PSA Progression, as defined by an increase in two consecutive measurements that fulfills all the following criteria: 1. The evaluations were performed with a minimum interval of 1 week. 2. Progressive worsening with an increase of at least 50% compared to baseline. 3. The minimum value of PSA is ≥ 1 ng/ml.